Assembly for a turbomachine turbine

ABSTRACT

The invention concerns an assembly for a turbomachine turbine, comprising a housing ( 1 ) extending circumferentially about an axis X, sectors ( 2 ) intended to form a ring capable of delimiting a gas flow path, each sector ( 2 ) comprising a first side ( 17 ) and a second side ( 18 ) extending radially and circumferentially about the said axis X and spaced axially from each other, each side ( 17, 18 ) of the sector ( 2 ) comprising at least one radial bearing surface capable of cooperating with radial bearing means ( 13, 14 ) of the housing ( 1 ), at least one of the sides ( 17, 18 ) comprising means ( 23 ) for the circumferential positioning of the sector ( 2 ) with respect to the housing ( 1 ), characterised in that each radial bearing surface is cylindrical of axis X and is capable of bearing on a complementary cylindrical surface of axis X, integral with the housing ( 1 ).

TECHNICAL FIELD OF THE INVENTION

The present invention relates to an assembly for a turbomachine turbine, in particular a high pressure turbine.

PRIOR ART

The field of application of the invention is in particular that of turbojet or turboprop aircraft. However, the invention is applicable to other turbomachines, such as industrial turbines.

The invention relates in particular to an assembly comprising a housing extending circumferentially about an axis and sectors intended to form a ring capable of delimiting a gas flow path so as to channel the flow of combustion gases. In particular, the sectors may comprise an abradable material in the radially inner part and be made of a ceramic matrix composite material, or CMC.

In the following, the terms ‘axial’, ‘radial’ and ‘circumferential’ are defined in relation to the axis of the housing.

Ceramic matrix composites, or CMCs, are known for their good mechanical properties, which make them suitable for use as structural elements, and for their ability to maintain these properties at high temperatures. In aircraft turbomachinery in particular, improved efficiency and reduced emissions are leading to the need to operate at ever higher temperatures. Therefore, the use of CMC for various hot parts of such engines has already been considered, especially since CMC has a lower density than traditionally used refractory metals.

Each sector typically comprises a radially inner cylindrical wall, intended to delimit part of the gas flow path, and two axially spaced sides extending radially outwards from the inner cylindrical wall. The inner wall may comprise a coating of abradable material, as is known per se. One of the sides of the housing typically has two circumferentially extending elongated holes spaced circumferentially from each other. The other side of the housing typically has a circumferentially extending elongated hole and a radially extending elongated hole, the two holes being spaced circumferentially from each other.

Each side of the sector can be mounted on a radial flange integral with the housing, by means of pins engaged in the recesses of the housing flanges and in the oblong holes of the corresponding sector. Such an assembly is isostatic, due to the presence of elongated holes and the orientation of these holes. However, since the pins are cylindrical, the contact areas between the pins and the edge of the sector slots are formed by lines. Such line contacts between the pins and the sector generate high Hertz pressures, causing premature wear of the sector by matting or “fretting” during operation.

The document EP 2 784 269 discloses a turbine ring sector comprising pins of elliptical cross-section and pins of rectangular cross-section, engaged in holes in the housing. Due to the clearance between the holes and the pins, and due to positioning and manufacturing tolerances, the contact areas between the pins of the sector and the holes in the housing remain limited. Furthermore, such tolerances also prevent precise radial positioning of the sector with respect to the housing.

The invention aims to remedy such drawbacks in a simple, reliable and inexpensive way.

SUMMARY OF THE INVENTION

To this end, the present invention concerns an assembly for a turbomachine turbine, comprising a housing extending circumferentially about an axis X, sectors intended to form a ring capable of delimiting a gas flow path, each sector comprising a first side and a second side extending radially and circumferentially about the said axis and spaced axially from each other, each side of the sector comprising at least one radial bearing surface capable of cooperating with radial bearing means of the housing, at least one of the sides comprising means for the circumferential positioning of the sector with respect to the housing, characterized in that each radial bearing surface is cylindrical of axis X and is capable of bearing on a complementary cylindrical surface of axis X, integral with the housing.

The use of large diameter cylindrical contact surfaces maximises these contact surfaces and thus reduces the Hertz pressures so as to avoid the aforementioned phenomena of premature wear by matting or “fretting”. The term ‘cylindrical’ can be used to define a surface of a part of a cylinder. The term ‘cylinder’ here defines a surface of revolution with a circular cross-section.

The cylindrical contact surfaces integral with the housing may be integrally formed with the housing or may be formed by one or more elements separate from the housing and integral with the housing.

The radial bearing surfaces of each side allow the sector to be positioned radially with respect to the housing, the sector being further positioned circumferentially by the corresponding means, said bearing surfaces and circumferential positioning means being adapted to ensure an isostatic mounting.

The first side may comprise first and second circumferentially extending elongated holes spaced circumferentially from each other, the second side comprising a third circumferentially extending elongated hole and a fourth radially extending elongated hole, the third and fourth elongated holes being spaced circumferentially from each other, first, second, third and fourth support pins integral with the housing being engaged respectively in the first, second, third and fourth oblong holes of the sector, the first, second and third pins being capable of bearing radially on the edges of the first, second and third holes, at the level of cylindrical surfaces of axis X.

It is possible to reverse the position of the pins and holes. In other words, the holes can be formed on the housing, while the pins can be formed on the sides of the sector.

The assembly may comprise holding means capable of holding the complementary bearing surfaces of the first, second and third pins of the housing against, respectively, the cylindrical bearing surfaces of the first, second and third oblong holes of the sector.

Such a feature allows the assembly to be produced and assembled with low tolerances. In fact, the holding means allow the cylindrical bearing surfaces of the pins and the corresponding oblong holes to be pressed against each other in the event of radial play between the pins and the said holes, and thus avoid any wear phenomenon.

The first and second pins may be integrally formed with a first support member mounted on the housing, the third pin being integrally formed with a second support member mounted on the housing.

The fourth pin may be integrally formed with the second support member.

The first and second support members may be identical in shape. This reduces the number of separate parts to be made and facilitates the assembly of such an assembly.

The fourth pin may be separate from the second support member.

The fourth pin is, for example, integral with a flange attached to the housing.

The first and second support members can be mounted, respectively, in recesses of a first flange and of a second flange which are integral with the housing.

Each support member may have an arc-shaped part of X-axis, from which the corresponding pin(s) extends, said arc-shaped part being mounted in a groove-like recess of X-axis of the corresponding flange.

One of the flanges may be integrally formed with the housing, the other flange being separate from the housing and fixedly mounted on the housing.

The flange is mounted on the housing by means of screws, for example.

The assembly may include means for circumferentially positioning each support member relative to the housing.

The said circumferential positioning means are, for example, formed by positioning pins mounted in holes in the support members and in flanges integral with the housing.

The invention will be better understood and other details, characteristics and advantages of the invention will appear when reading the following description, which is given as a non-limiting example, with reference to the attached drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 and

FIG. 2 are perspective views of a rotor sector and part of the stator of an assembly according to a first embodiment of the invention;

FIG. 3 is a cross-sectional view in a radial plane, showing the mounting of the first and second pins in the corresponding side of a sector;

FIG. 4 is a cross-sectional view in a radial plane, showing the mounting of the third and fourth pins in the corresponding side of a sector,

FIG. 5 and

FIG. 6 are half sectional views in an axial plane, before and after mounting the removable flange on the housing respectively;

FIG. 7 and

FIG. 8 are views corresponding to FIGS. 1 and 2 respectively, illustrating a second embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 to 6 show an assembly for a turbomachine turbine, comprising a housing 1 extending circumferentially about an axis to be noted X (not shown), and contiguous sectors 2 intended to form a ring capable of delimiting a gas flow path. Only one sector 2 is shown in the figures, and only part of the housing 1 is shown.

The housing 1 comprises a first flange 3 and a second flange 4 extending radially inwards from an annular part 5. The first flange 3 is here made of a separate part, fixed to the housing 1, for example by screwing.

Each flange 3, 4 has annular grooves 6 of axis X, opening axially opposite the opposite flange 4, 3. Each groove 6 is delimited by a flat, radial annular bottom surface 6 a and two axially extending cylindrical side surfaces 6 b. Holes 7 are provided in the bottom surfaces 6 a of the grooves 6, with a cylindrical circumferential positioning pin 8 engaged in each hole 7. The pins 8 of each flange 3, 4 may have different dimensions, although they have the same reference 8.

First support members 9 and second support members 10 are mounted on the first flange 3 and the second flange 4 respectively.

In particular, each support member 9, 10 has an arc-shaped part 11, from which two pins 12, 13, 14, 15 extend axially, the two pins 12, 13 or 14, 15 being spaced circumferentially from each other. The pins 12 to 15 are located at the circumferential ends of the arc-shaped part 11. The first support member 9 thus comprises first and second pins 12, 13. The second support member 10 thus has third and fourth pins 14, 15.

Each pin 12 to 15 has a radially outer cylindrical surface 16 b (or part of a cylinder) with an X-axis, a radially inner cylindrical or flat surface 16 a with an X-axis and two radially extending side surfaces 16 c (FIG. 3). The arc-shaped part 11 of the first support member is mounted in the groove 6 of the first flange 3. The arc-shaped part 11 of the second support member is mounted in the groove 6 of the second flange 4. The arc-shaped part 11 of each support member 9, 10 has a hole 11 c (FIGS. 1 and 2) in which the corresponding pin 8 is engaged. The radial dimension of each arc-shaped part 11 corresponds to the radial dimension of the corresponding groove 6. The radially inner and outer edges 11 a, 11 b of each part 11 are thus capable of bearing on the corresponding side surfaces 6 b of the grooves 6, so as to effectively take up the radial forces in operation. s The pins 8 are able to absorb circumferential forces, although these forces are relatively small.

Each ring sector 2 has a cylindrical wall 19 (or part of a cylinder) from which two sides 17, 18 extend radially outwards, respectively a first side 17 on the first flange 3, and a second side 18 on the second flange 4. The radially inner surface 19 a of the cylindrical wall 19 may comprise a coating of abradable material, as is known per se. Said radially inner surface 19 a is intended to delineate a part of the gas flow path within the high pressure turbine of the turbomachine. Each side 17, 18 extends circumferentially around the entire circumference of the sector 2.

The first side 17 has circumferentially extending first and second elongated holes 20, 21 spaced circumferentially from each other. The second side 18 has a third circumferentially extending slotted hole 22 and a fourth radially extending slotted hole 23, the third and fourth slotted holes 22, 23 being spaced circumferentially from each other.

The radially inner ends of the sides 17, 18 have rounded material protrusions 24 opposite the slotted holes 20 to 23.

The radially inner and outer edges 25 a, 25 b (FIG. 3) of the first, second and third holes 20, 21, 22 are formed by cylindrical (or part-cylindrical) surfaces of axis X.

The side edges 25 c of the fourth hole 23 are radially oriented (FIG. 4). The first, second, third pins 12, 13, 14 may be engaged with no or minimal radial clearance between the radially inner and outer edges 25 a, 25 b of the first, second and third holes 20, 21, 22, respectively.

The fourth pin 15 may be engaged with no or minimal circumferential clearance between the side edges 25 c of the fourth hole 23.

A greater radial clearance can be provided between the first, second and third pins 12, 13, 14 and the first, second and third holes 20, 21, 22 to allow less restrictive dimensional and mounting tolerances. In such a case, it is possible to provide holding means capable of holding the complementary bearing surfaces of the first, second and third pins 12, 13, 14 of the housing 1 against, respectively, the cylindrical bearing surfaces 25 a, 25 b of the first, second and third oblong holes 20, 21, 22 of the sector 2.

The first, second and third pins 12, 13, 14 can come to bear on the radially inner edges 25 a or preferably on the radially outer edges 25 b of the first, second and third slotted holes 20, 21, 22, here on the radially outer edges 25 b.

When the sectors 2 are mounted in the housing 1, each second support member 10 is mounted in the groove 6 of the second flange 4, and the third and fourth pins 14, 15 of each second support member 10 are engaged in the third and fourth holes 22, 23 of each sector 2, as illustrated in FIG. 5. The first support members 9 are mounted in the groove 6 of the first flange 3, the latter being annular and formed in one piece, or sectorised.

The first flange 3 is then mounted on an annular support flange 26 of the housing 1 and secured to said housing 1, for example by screwing, as shown in FIG. 6. The annular flange 26 extends radially inwards from the annular part 5 of the housing 1. When the first flange 3 is fitted, the first and second pins 12, 13 of the first support member 9 are inserted into the first and second holes 20, 21 of the corresponding sector 2. The radial holding means (not shown) then hold the pins 12 to 14 against the radially outer edges 25 b of the holes 20 to 22 of the sector 2.

FIGS. 7 and 8 illustrate a second embodiment, which differs from that previously shown with reference to FIGS. 1 to 6 in that the second support member 10 is without a fourth pin 15. The sector 2 is held in place circumferentially by the cylindrical pin 8, which is mounted in a complementary hole 7 in the second flange 4 and in the fourth hole 23 in the sector 2, for example through an opening, a notch 27 or a hole in the second support member 11. The pin 8 can be formed integrally with the second flange 4.

Furthermore, as before, the said pin 8 ensures that the second support member 10 is held in its circumferential position.

In the two embodiments presented, the use of cylindrical contact surfaces 16 b, 25 b of large diameter, i.e. of a diameter corresponding to the diameter of the pins 12 to 14 in relation to the axis X, makes it possible to maximise the said contact surfaces 16 b, 25 b and to reduce the Hertz pressures in such a way as to avoid the aforementioned phenomena of premature wear of the sectors 2 by matting or “fretting” 

1.-9. (canceled)
 10. An assembly for a turbomachine turbine, comprising a housing (1) extending circumferentially about an axis X, sectors (2) intended to form a ring capable of delimiting a gas flow path, each sector (2) comprising a first side (17) and a second side (18) extending radially and circumferentially about the said axis X and spaced axially from each other, each side (17, 18) of the sector (2) comprising at least one radial bearing surface (25 b) capable of cooperating with radial bearing means (12, 13, 14) of the housing (1), at least one of the sides (17, 18) comprising means (23) for the circumferential positioning of the sector (2) with respect to the housing (1) characterised in that each radial bearing surface (25 b) is cylindrical of axis X and is capable of bearing on a complementary cylindrical surface of axis X (16 b), integral with the housing (1), and in that the first side (17) comprises first and second oblong holes (20, 21) extending circumferentially and spaced circumferentially from each other, the second side (18) comprising a third oblong hole (22) extending circumferentially and a fourth oblong hole (23) extending radially, the third and fourth oblong holes (22, 23) being spaced circumferentially from each other, first, second, third and fourth support pins (12, 13, 14, 15) integral with the housing (1) being engaged respectively in the first, second, third and fourth oblong holes (20, 21, 22, 23) of the sector (2), the first, second and third pins (12, 13, 14) being capable of coming to bear radially on the edges of the first, second and third holes (20, 21, 22), at the level of cylindrical surfaces (16 b, 25 b) of axis X.
 11. An assembly according to claim 10, characterized in that it comprises holding means capable of holding the complementary bearing surfaces (16 b, 25 b) of the first, second and third pins (12, 13, 14) of the housing (1) against, respectively, the cylindrical bearing surfaces (25 b) of the first, second and third oblong holes (20, 21, 22) of the sector (2).
 12. An assembly according to claim 10, characterised in that the first and second pins (12, 13) are integrally formed with a first support member (9) mounted on the housing (1), the third pin (14) being integrally formed with a second support member (10) mounted on the housing (1).
 13. An assembly according to claim 11, characterised in that the first and second pins (12, 13) are integrally formed with a first support member (9) mounted on the housing (1), the third pin (14) being integrally formed with a second support member (10) mounted on the housing (1).
 14. An assembly according to claim 12, characterised in that the fourth pin (15) is integrally formed with the second support member (10).
 15. An assembly according to claim 12, characterised in that the fourth pin (15) is separate from the second support member (10).
 16. An assembly according to claim 12, characterised in that the first and second support members (9, 10) are mounted, respectively, in recesses (6) of a first flange (3) and of a second flange (4) which are integral with the housing (1).
 17. An assembly according to claim 14, characterised in that the first and second support members (9, 10) are mounted, respectively, in recesses (6) of a first flange (3) and of a second flange (4) which are integral with the housing (1).
 18. An assembly according to claim 15, characterised in that the first and second support members (9, 10) are mounted, respectively, in recesses (6) of a first flange (3) and of a second flange (4) which are integral with the housing (1).
 19. An assembly according to claim 16, characterised in that each support member (9, 10) has an arc-shaped part (11) of X-axis, from which the corresponding pin(s) (12, 13, 14, 15) extend(s), said arc-shaped part (11) being mounted in a groove-like recess (6) of X-axis of the corresponding flange (3, 4).
 20. An assembly according to claim 16, characterised in that one (4) of the flanges (3, 4) is integrally formed with the housing (1), the other flange (3) being separate from the housing (1) and fixedly mounted on the housing (1).
 21. An assembly according to claim 19, characterised in that one (4) of the flanges (3, 4) is integrally formed with the housing (1), the other flange (3) being separate from the housing (1) and fixedly mounted on the housing (1).
 22. An assembly according to claim 12, characterized in it comprises means (8) for the circumferential positioning of each support member (9, 10) with respect to the housing (1).
 23. An assembly according to claim 14, characterized in it comprises means (8) for the circumferential positioning of each support member (9, 10) with respect to the housing (1).
 24. An assembly according to claim 15, characterized in it comprises means (8) for the circumferential positioning of each support member (9, 10) with respect to the housing (1).
 25. An assembly according to claim 16, characterized in it comprises means (8) for the circumferential positioning of each support member (9, 10) with respect to the housing (1).
 26. An assembly according to claim 19, characterized in it comprises means (8) for the circumferential positioning of each support member (9, 10) with respect to the housing (1).
 27. An assembly according to claim 20, characterized in it comprises means (8) for the circumferential positioning of each support member (9, 10) with respect to the housing (1). 